Agilent 5975B MSD (problem with pump down process)

[Nicοlas]

Hi

I have a problem with the Agilent 5975B MSD. It fails to complete the pump down process. The foreline pressure and the foreline pump seems to be ok but the temperature of ion source and quadrupole remain at room temperature (25 °C).
I also get the following message <high Vacuum Pump Off>.
practically the pump down process never completes (does not stop but continues indefinitely).
Foreline pressure reaches 53 mTorr but the temperatures of ion source and quadrupole are always the same.

thanks for your attention

Nicolas

[Don Baker]

Please understand that I'm not an expert in this

It sound to me that your high vacuum pump - whether diffusion pump tubo pump or whatever - has not turned on. 53 x 10^-3 torr is nowhere near a low enough pressure. The machine is most likely preventing the electronics from turning on because the pressure is too high. Mine has an interlock that prevents the electronics from powering up unless the pressure is good.

What kind of high vaccum pump do you have?
If turbo - can you hear it spin up?
If diffusion - are you sure the heater is working?

Just some guesses.
If anyone else here says anything contray to what I have said, they are probably right. I am just learning this stuff myself.

Don Baker

[Nic&#959;las]

i have a diffusion pump. you mean the heater of the diffusion pump or the heater of ionic source? the diffusion pump remains cold during the pump down process so i guess that the heater does not heat the pump.

I can't locate where the problem is. if the pressure is not low enough the diffusion pump remains turned off, but the heater of ion source and quadrupole should be active. in my case, all the temperature sensors indicates the same temperature(25 Celsius).

i am a little confused..

Nicolas

[Don Baker]

This is from a 5970 manual, not a 5975, but because they are from the same company, a similar design approach is likely. The 5970 uses a turbomolecular pump, but regardless of the high vacuum pumping method, the concepts are the same.

<begin fair use, copyright Hewlett-Packard Company>
The vacuum system is controlled by the turbo controller. When proper vacuum has been achieved, the manifold heater relay can be activated. That, in turn, allows the detector electronics to be turned on so that the MSD can be used.
...

The Heater/Electronics switch enables the manifold heater and the electronics but does NOT necessarily turn them on. The heater and electronics will turn on only after the turbomolecular pump reaches 50% of its maximum speed.
<end fair use>

There are no moving parts in a diffusion pump, so the speed of the pump can not be measured as it was with the 5970. But if the 5975 was designed in a manner similar to the 5970, the engineers would have placed some similar criterion on the state of the high vacuum system, quite possibly by measuring pressure or by sensing some other aspect of the diffusion pump operation.

There should be a heater at the bottom of your diffusion pump. You should be able to find it by looking for a fairly heavy duty electrical connection. The diffusion pump most likely also has a cooling jacket (and possibly a cold trap at the top) so, other than the heater area, it may feel cool.

Make sure that the diffusion pump is getting power. If it is, and the pump is cold, then you may have a problem with the pump's heater. If the heater is not getting power, then something is not allowing the heater to come on. Perhaps a failed relay, perhaps a loose wire, perhaps failed electronics. I would have to see a schematic to venture any more of a guess.

Don Baker

[Ron]

Are you sure that the heater will turn on if the diffusion pump is not operating? I would suspect there is an interlock that allows the heaters to turn on after the diffusion pump is up to temperature. It has been a long time since I have used a diffusion pump system, but turbo pump systems abort the pump down process if the turbo isn't up to speed after a specific time.

I suspect that you may have a blown fuse in the heater circuit that is preventing the pump from heating. There are other possible causes, but I would start with the simple things like cables connected properly and fuses.

[Nic&#959;las]

so far i have identified two fuses and i test them. Are precisely the two fuses in the back side of the msd. Seems that they working correctly. I have no idea of others fuses.
the phrase <blown fuse in the heater circuit (Don)> it made me dream a happy end.. but how can i locate them ??
An other interesting observation. The foreline pressure reaches 55 mTorr, pressure that the instrument should be READY to operate. This fact should mean that the foreline pump is on but at the same time COLD! Besides this, ion source and quadrupole temperatures still at 25 Celsius.



Nicolas...needs HELP

[bhuvfe]

Nicolas,

When was the last time the system worked?
Have you recently done some maintenance on it?

I have only one diffusion pump GC-MS and the only problems I ever had where connection related (check if everything is plugged where is supposed to, e.g. on the back of the MSD) or fans related (not applicable here).

Check also this document:
http://www.chem.agilent.com/Library/Sup ... a20415.pdf

I don't know on a 5975 but on a 5972 you get some response from the diffusion pump (e.g. error messages such as "too cold" or "too hot"). Can you see anything similar on your system ?



Good luck.

bhuvfe

[Rick]

If your pressure is 53mtorr,your mechanical pump is ok and your diffusion pump is ok....normally, the base of diffusion pump base will be hot.
I suspect the wire of ion source and quadrupole heater, or a connection or a temperature limit not properly set or a problem with the side board.

[Nic&#959;las]

bhuvfe,


nothing like <error messages "too cold" or "too hot"> the only message IS <high Vacuum Pump Off>.

the last time that the system worked was one month ago. it was in standby mode and suddenly appear the pump down message on the screen of MSD. since then it cant complete the pump down process..

i cant understand what happens..

[Rick]

If you have a foreline vacuum of 53mtorr, your diffusion is ok...approch your hand near the base of your diffusion pump....hot or cold?

[Nic&#959;las]

rick,

i think that its cold but am not sure. i have never touch it but i saw the oils level on too cold position.

[bhuvfe]

rick,

i think that its cold but am not sure. i have never touch it but i saw the oils level on too cold position.

When the pump is hot we are talking about T at the bottom of it above 100 C (on mine around 150-160 C) so your pump seems to be cold.


If you find no cable disconected between the diffusion pump and the MSD it might be something for a service engineer.


Have you tried to switch off, wait few seconds, and then on again the MSD? It seems that if the supply voltage falls below a certain minimum for 4 seconds the pump shut off (at least on my old system) and power cycle it is the only way to reset it. Did you have power failures in your lab recently?

[Rick]

If your oil level is at cold position, your diffusion pump is off or your oil quantity have a problem.
Touch the base of your diffusion pump with your finger.....cold or hot?
53mtorr is a good vacuum, so, i think that your diffusion pump is running, so check if it's cold or hot first for investigate the problem.

If your diffusion is really cold, check for the connection between MSD and Diffusion pump
If the pump is hot, the problem is probably a sensor

Let me know!

good luck

[Don Baker]

Can someone straighten me out on something here?

In my book, 53 mTorr, 5.3 x 10^-2 Torr, is OK for the foreline pressure, but that is more than four orders of magnitude higher pressure than my machine operates at. How can you say that the diffusion pump is operating properly if the vacuum is 53 mTorr? My ion gauge won't even operate at a pressure that high. My machine is supposed to operate at a pressure of about 1 x 10^-6 Torr.

What am I missing in this discussion?

Don Baker

[Ron]

You're not missing anything. The foreline pressure is at 53 mTorr, but there is no high vacuum reading given. From the foreline pressure we know the rotary pump is ok, but don't know anything about the status of the diffusion pump. I would assume that the 5975 has an interlock so you can't turn on the high vacuum gauge unless the high vacuum system is fully operational.